1. Field of the Invention
The present invention relates to a liquid discharge apparatus and a liquid discharge device group.
2. Discussion of the Background
As shown in FIG. 13, an inkjet apparatus of a printer includes a nozzle hole 201 through which fluid (liquid ink) is discharged, a pressure chamber 202, a supply passage 203, and a fluid supply chamber 204 which are formed in a head body 207 by means of photo-etching or the like. The inkjet apparatus further includes a diaphragm 205 to cover an upper opening of the pressure chamber 202 and an actuator 206 for moving the diaphragm 205 up and down. Liquid ink is supplied to the fluid supply chamber 204 through a supply inlet 204a and is then supplied to the pressure chamber 202 through supply passage 203 so that the pressure chamber 202 and the nozzle hole 201 are filled with the liquid ink.
To conduct printing by the inkjet apparatus, the diaphragm 205 is moved up and down by causing the actuator 206 to vibrate up and down so that the pressure of the fluid inside the pressure chamber 202 varies. As the inner pressure of the pressure chamber 202 is increased by the downward movement of the diaphragm 205, the inner fluid (liquid ink) is discharged from an end opening 201a of the nozzle hole 201. When the inner pressure of the pressure chamber 202 is increased, the inner fluid is not only discharged through the nozzle hole 201 but also flowing back into the fluid supply chamber 204 at the same time. In the inkjet apparatus, therefore, the supply passage 203 is structured to have a reduced cross-section (throttled) in a passage connecting the pressure chamber 202 and the fluid supply chamber 204 so as to provide fluid resistance to the aforementioned back flow. Generally, it is designed to make the fluid resistance in the supply passage 203 substantially equal to the fluid resistance in the nozzle hole 201.
On the other hand, as the diaphragm 205 is moved upward by the actuator 206, the diaphragm 205 operates to increase the volume of the pressure chamber 202 so as to decrease the inner pressure. During this, fluid in the nozzle hole 201 is sucked toward the pressure chamber 202. However, meniscus is formed because of the surface tension of fluid at the end opening 201a, thereby preventing air from being sacked into the pressure chamber 202. At the same time, fluid in the fluid supply chamber 204 is sucked through the supply passage 203 and is supplied into the pressure chamber 202. Inkjet apparatuses as mentioned above are disclosed, for example, in Japanese Unexamined Patent Application Publications Nos. 2005-47165 and 2005-67047. The contents of these publications are incorporated by reference in their entirety.